Stereoscopic imaging systems have been employed to give a three-dimensional appearance to field sequential images displayed on a video display screen. The three-dimensional appearance is created by active stereoscopic glasses that switch between opaque and transmissive optical states to alternately transmit to a viewer left- and right-eye views of a stereoscopic image that is sequentially displayed on the screen. The viewer fuses the separate left- and right-eye views into a single stereoscopic image.
In certain prior stereoscopic imaging systems, the active stereoscopic glasses are linked to the video display with wires. This is undesirable, however, because the wires tether the viewer to the video display. To overcome this problem, other stereoscopic imaging systems have used electromagnetic radiation to link the stereoscopic glasses to the video display. For example, U.S. Pat. No. 4,967,268 of Lipton et al. ("Lipton et al. patent"), entitled "Liquid Crystal Shutter System for Stereoscopic and Other Applications," describes electromagnetically linked active stereoscopic glasses.
In the system of the Lipton et al. patent, the transmitted electromagnetic signal includes pulse width modulated information. As shown in FIG. 10 and described in col. 7, lines 30-68 of the Lipton et al. patent, the electromagnetic signal includes a 61 microsecond start pulse. If the electromagnetic signal continues for an additional 61 microseconds following the start pulse, the signal receiver circuitry causes the left-eye piece to be transmissive and the right-eye piece to be opaque. If the electromagnetic signal is not present for the next 61 microseconds following the start pulse, the signal receiver circuitry causes the right-eye piece to be transmissive and the left-eye piece to be opaque. The demodulating circuitry employed in the signal receiver circuitry creates unnecessary complexity and expense.
There is a need, therefore, for electromagnetically linked stereoscopic glasses that do not employ demodulating circuitry.